1. Field of the Invention
The present invention relates to a method of manufacturing a field-emission-type electron emission source using a carbon nanotube layer as an electron emission portion.
2. Description of the Background Art
An electron emission source for FED (Field Emission Display) has conventionally been manufactured. In the method of manufacturing the electron emission source, initially, a cathode electrode is formed on a substrate. Then, a carbon nanotube layer serving as an electron emission portion is formed on the cathode electrode. Thereafter, an insulating layer is formed to cover an exposed surface of the cathode electrode and an exposed surface of the carbon nanotube layer, and a gate electrode is formed on the insulating layer. Thereafter, an opening is formed in the gate electrode, and an opening is formed in the insulating layer under the opening in the gate electrode. An upper surface of the carbon nanotube layer is thus exposed.
In forming an opening in the insulating layer described above, reactive ion etching (RIE) representing dry etching is employed. In forming an opening in an insulating film using RIE, however, RIE is performed even when the carbon nanotube layer is exposed. Consequently, the exposed surface of the carbon nanotube layer is damaged. In addition, unnecessary deposits adhere to the exposed surface of the carbon nanotube layer as well as to an inner side surface of the opening in the insulating layer. On the other hand, according to a technique to form the opening in the insulating layer using wet etching, it is difficult to control a shape of the opening in the insulating layer. For the reasons as described above, the conventional methods of manufacturing the electron emission source are disadvantageous in their inability to improve electron emission performance of the carbon nanotube layer.
As one technique to solve the above-described problem, necessity of some kind of process for the exposed surface of the carbon nanotube layer in order to improve the electron emission performance thereof has generally been known. For example, the inventors of the subject application have confirmed that a method of irradiating the carbon nanotube layer with laser beam is effective for a case in which the carbon nanotube layer is employed. This is because, when a plurality of long carbon nanotubes are entangled and raising of the carbon nanotubes is not easy, long carbon nanotubes are cut as a result of irradiation with laser so that a large number of short carbon nanotubes that are more readily raised are formed.
If intensity of the laser emitted to carbon nanotube particles is excessively high, however, the gate electrode of the FED is broken down. In addition, some of the carbon nanotube particles leave the bottom surface of a hole formed to penetrate the insulating layer. Accordingly, the carbon nanotube particles are scattered in the hole and adhere to a sidewall of the hole. Consequently, short-circuiting occurs between the gate electrode and the cathode electrode. Meanwhile, if the intensity of the laser is low, little improvement in the electron emission performance of the carbon nanotube layer is achieved.